Amorphous-Nanocrystalline Fluorinated Halide Electrolytes with High Ionic Conductivity and High-Voltage Stability

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• All-solid-state sodium-ion batteries (ASSSIBs) are a promising alternative to lithium-ion batteries due to cost and scalability.
• Development of ASSSIBs is hindered by the need for solid electrolytes with superior ionic conductivity, electrochemical stability, and interfacial properties.

Purpose of the Study:

• To develop a novel fluorine-doped halide solid electrolyte for high-performance ASSSIBs.
• To investigate the impact of fluorine doping on the structure, ionic conductivity, and electrochemical stability of the solid electrolyte.
• To evaluate the performance of the developed electrolyte in a complete ASSSIB device.

Main Methods:

• Synthesis and characterization of a fluorine-doped halide solid electrolyte (2NaF-ZrCl4, 2-NFZC) with an amorphous-nanocrystalline structure.
• Electrochemical testing including ionic conductivity measurements and cycling performance evaluation in an ASSSIB.
• Analysis of interfacial compatibility and reaction suppression using specific electrode materials.

Main Results:

• The 2-NFZC electrolyte exhibits high ionic conductivity (2.35 × 10⁻⁴ S cm⁻¹ at 25 °C) and good high-voltage stability.
• Fluorine doping enhances Na-ion transport by promoting Zr-F bonding and minimizing Na-F interactions.
• The ASSSIB utilizing 2-NFZC achieved a discharged capacity of 137.1 mAh g⁻¹, 81.1% capacity retention over 600 cycles, and reduced interfacial side reactions.

Conclusions:

• Fluorine doping is an effective strategy for designing advanced solid electrolytes for ASSSIBs.
• The developed 2-NFZC electrolyte demonstrates significant potential for enabling high-performance and stable all-solid-state sodium-ion batteries.
• This work contributes to the advancement of next-generation energy storage solutions.